1. Field of the Invention
The present invention relates generally to an arrangement for indicating revolutional speed of a revolving body, and more particularly, to a revolutional speed indicator arrangement for use in record players for visually indicating whether or not revolutional speed of a turntable differs from a reference speed.
2. Description of the Prior Art
In order to determine how revolutional speed of a revolving body differs from a difference speed, the stroboscopic method has been utilized in the prior art. In the conventional stroboscopic method, a record player turntable, for example, is provided with a stroboscopic pattern of stripes along the circumference thereof, which pattern is illuminated by a neon tube flashing at a predetermined frequency. When the turntable rotates at a rotating speed equal to a reference speed, such as 331/3 rpm, the stroboscopic pattern appears as if it were still. If the turntable runs faster than the reference speed, then one can visually recognize that the pattern is running in the revolutionary direction of the turntable. On the other hand, if the revolutionary speed of the turntable becomes lower than the reference speed, then the observer will see the stroboscopic pattern running in the reverse direction to the revolution of the turntable.
The speed at which the stroboscopic pattern appears to run as the turntable rotates is associated with a difference between the revolutional speed of the turntable and the reference speed. If such a difference is significantly large, the appearance of the pattern of stripes under the storoboscopic light can easily be recognized at a glance. However, when the difference between the revolutional speed of the turntable and the reference speed is sufficiently small, it is very difficult for the observer to determine whether or not the difference exists. In addition, the provision of such stroboscopic patterns of stripes in the circumference of turntables is undesirable from industrial design standpoint.